I've often written about foam being better than batts. In a concrete basement below grade there will be no air pressure differential to cause air movement from the outside in. Batts are OK here. The bathroom is not going to be sealed from the rest of the house, so whether the batts are faced or not is not a big deal. That is my view. Others may be more precise about reasons for one or the other. Definitely do insulate. It's a more comfortable room afterwards. The temperature gradient is lessened. Batts are OK. Any kind of batt. If you want to do somthing better, you could use spray foam but that is a whole new learning curve. Batts are easy. Methinks a little knowledge can be a dangerous thing.

I am redoing the upstairs bathroom. It is in a brick and block house with NO insulation on the exterior wall. The exterior wall is furred with 1x5 to attach the original wire mesh and mud for tile. The wall has a 36x36 rough opening window. The tub is to be placed against the exterior wall. I have some issues that I want to address when installing the new tub/shower: - Because of the original tiling method that led to very thick mud and tile, I have a lot of space to make up on the ends of the tub (1.5-2 inches, walls not square) - I want to install at least a little insulation. My thought is to fill the gaps between the furring strips on the exterior wall with 3/4 inch thick rigid foam insulation which is essentially the thickness of the 1x5 furring strips. The rigid insulation is in several strips, none wider than 12 inches. The rigid foam covers less than 50% of the wall, and most of it is below the tub lip. The tub lip would then be butted against the foam. Above the tub lip (not touching it) would be a sheet of exterior grade plywood run horizontally and hanging over the tub lip. Then vapor barrier, durarock (with taped seems), thinset, and tile. The plywood would provide some limited insulation (relative to furring strips over a block wall) and provide more wood depth and screw placement options to attach the durarock. This would be more along the lines of Mongoct posts which had the durarock fully inside the lip of the tub (my understanding of Mongoct posts). I cannot build a 2x3 or 2x4 wall inside the exterior wall because there is insufficient space to the toilet (unless I move the toilet drain which in turn requires cutting a joist in an already small bathroom). As an aside, based on a Fine Homebuilding article, I was also installing insulation on all of the bathroom walls to help sound proof the bathroom from the adjacent bedrooms. I placed the rigid insulation against the bedroom walls. The insulation is often in multiple pieces in order to get it behind exiting fire blocking, wiring, outlets, So I have two questions concerning the exterior wall: - Is there any risk that the limited rigid foam insulation may act as a second vapor barrier and cause moisture/mold issues. - Is there any issue using full sheets of plywood as the furring. I have a third question related to the tub train. The tub we are installing (cast iron Toto) does not have the drain on the same center line as the previous tub. Thus I need to move the galvanized piping. I plan to cut the piping a few feet from the tub and replace with schedule 40 PVC. To join the PVC to galvanized pipe I was going to use a rubber boot with hose clamps (1.5 to 1.5 inch). (I really donÂt want to try to get galvanized pipe to line with the tub drain.) Is there an issue with this method to join the pipes? Is there a better method? Thanks for any help. Finally, I have read many of the very informative and helpful posts and appreciate the time, exceptional expertise, detailed/informative answers, and etiquette that has been displayed in this forum. Particularly note to Mongoct and Bill.

This is a pretty silly discussion. If your house is in violation of the building code, the building department won't care who did the work. If they take any action at all, you will be ordered to correct it, not the state; the town's authority is over you, not the state. If you want the state to fix it, you will have to ask them directly; if they refuse, you should forget about it and move on. Unless they are unusually stupid, they would have asked you to sign a waiver of responsibility before doing any work on your property; try reading that "receipt" you signed. The discussion of building code requirements is probably irrelevant if this house is in VT. If VT has finally adopted a residential building code I haven't heard about it. Unless this particular town has adopted it's own code I suspect it is perfectly legal to expose polystyrene insulation board in this house. And you thought NH was the Live Free or Die state. "Let's just 'ASSUME', for a moment, that the insulation can be left uncovered" It's ridiculous to assume something is OK that could kill your family (and the cat) before they could get out of the house in a fire. Do you understand what toxic smoke does to you? You canâÂÂt just run through it and cough a bit like Bruce Willis in a movie. "Overcome by smoke" means you can't get to safety on your own. After nearly a hundred people died primarily from toxic smoke from burning exposed polyurethane foam in a night club in Warwick RI in 2003 you would think that foam insulation would get more respect as a killer. My son lived a few miles away and didn't answer his phone so I drove there to see if he had been in the fire so it left an impression on me. The Station nightclub was required by state law to have sprinklers installed when it was converted from a restaurant to a night club but the local building and fire officials issued permits without enforcing that requirement. Despite the negligence of the local officials and the foam supplier, after a long court battle it was the owners of the property and the pyrotechnic equipment who went to prison. Put the safety of your family ahead of energy conservation, academic responsibility debates, or annoying pet behavior while you can.

Technically 1" of XPS versus 2" of XPS would be about half the cost. So, is that worth the savings ultimately? I will not have in floor radiant heat for the basement. When you say slab I keep thinking you mean a slab built house, to reiterate, this is a basement and local code *here at least* does not require ANY rigid foam for the basement slab. Not sure if it even is required on the foundation walls. I guess this zoning ordinance is behind on code updates. -shrug- I see myself as one in a few that will be considering rigid foam for any basement application in new construction here. Is there any benefit to using XPS over the EPS for the foundation WALLS? I know I can get some EPS cheaper per R-Value but it will be thicker. I was thinking over 2" of EPS foam would be troublesome to fasten and then cover. Any recommendations on what to cover the foam with before backfill? Or should I only worry about covering the exposed foam on the walkout basement portion? I intend on using a waterproofing prior to installing rigid foam to the foundation walls.